// Copyright 2004-2010 Castle Project - http://www.castleproject.org/
// 
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// 
//     http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

namespace Fas.Tem.Runtime.Parser.Node
{
    using Context;

    /// <summary>
    /// Handles the equivalence operator
    /// 
    /// &lt;arg1&gt;  == &lt;arg2&gt;
    /// 
    /// This operator requires that the LHS and RHS are both of the
    /// same Class.
    /// </summary>
    /// <version> $Id: ASTEQNode.cs,v 1.3 2003/10/27 13:54:10 corts Exp $ </version>
    public class ASTEQNode : SimpleNode
    {
        public ASTEQNode(int id) : base(id)
        {
        }

        public ASTEQNode(Parser p, int id) : base(p, id)
        {
        }

        /// <summary>Accept the visitor. *
        /// </summary>
        public override object Accept(IParserVisitor visitor, object data)
        {
            return visitor.Visit(this, data);
        }

        /// <summary>
        /// Calculates the value of the logical expression
        /// 
        /// arg1 == arg2
        /// 
        /// All class types are supported.   Uses equals() to
        /// determine equivalence.  This should work as we represent
        /// with the types we already support, and anything else that
        /// implements equals() to mean more than identical references.
        /// </summary>
        /// <param name="context"> internal context used to evaluate the LHS and RHS </param>
        /// <returns>
        /// true if equivalent, false if not equivalent,
        /// false if not compatible arguments, or false
        /// if either LHS or RHS is null
        /// </returns>
        public override bool Evaluate(IInternalContextAdapter context)
        {
            object left = GetChild(0).Value(context);
            object right = GetChild(1).Value(context);

            // for equality, they are allowed to be null references 
            try
            {
                if (ObjectComparer.CompareObjects(left, right) == 0)
                {
                    return true;
                }
            }
            catch
            {
                // Ignore, we can't compare decently by value, but we honestly don't give a sh*t
            }

            // They are not equal by value, try a reference comparison
            // reference equal => definitely equal objects ;)
            // For operator overloaded types, this will not really be a reference comp, but that's ok.
            return left == right;
        }
    }
}